1. Field of the Invention
The present invention relates to a mechanism for conducting data transmission from a network management entity or a communication network control element to a terminal or UE with improved robustness. Specifically, the present invention is related to an apparatus, a method and a computer program product which provide a communication mechanism in which an improved robustness of data communication can be achieved by using a multiflow connection between a network and a terminal.
2. Related Background Art
Prior art which is related to this technical field can e.g. be found in technical specifications according to 3GPP TS 25.308 (e.g. version 11.0.0), 3GPP TS 25.322 (e.g. version 10.1.0), and 3GPP TS 25.331 (e.g. version 11.0.0).
The following meanings for the abbreviations used in this specification apply:
AM: acknowledged mode
ARQ: automatic repeat request
BS: base station
CPC: continuous packet connectivity
CQI: channel quality indicator
DL: downlink
eSCC: enhanced SCC
F-DPCH: fractional dedicated physical channel
HARQ: hybrid ARQ
HS-DSCH: high speed downlink shared channel
HSPA: high speed packet access
LTE: Long Term Evolution
LTE-A: LTE Advanced
MAC: medium access control
MBMS: multimedia broadcast and multicast services
MF: multiflow
PDCP: packet data layer convergence protocol
PDU: protocol data unit
RLC: radio link control
RNC: radio network controller
RRC: radio resource controller
RSSI: received signal strength indicator
SCC: serving cell change
SGSN: serving GPRS support node
SHO: soft handover
SINR: signal to interference plus noise ratio
SRB: signalling radio bearer
Tr, TM: transparent mode
TX: transmission
UE: user equipment
UL: uplink
UM: unacknowledged mode
VoIP: voice over IP
In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), DSL, or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) and fourth generation (4G) communication networks like the Universal Mobile Telecommunications System (UMTS), enhanced communication networks based e.g. on LTE or LTE-A, cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolution (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN), Bluetooth or Worldwide Interoperability for Microwave Access (WiMAX), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WiMAX Forum and the like are working on standards for telecommunication network and access environments.
Generally, for properly establishing and handling a communication connection between communication elements or terminals such as a user equipment (UE) and another communication element, terminal or user equipment, a database, a server, etc., one or more intermediate network elements such as communication network control elements, network management entities, support nodes or service nodes are involved which may belong to different communication network.
For achieving a more efficient way for using network resources, multi-point transmission schemes are employed. For example, in 3GPP based networks according to release 11, for example, HSDPA multiflow transmission is under discussion where users (UEs) being on a cell edge are provided with improved data rates by receiving transmissions also from neighbouring cells.
For example, at a cell edge, where also multiflow operates, UEs may occasionally experience very poor radio performance. For best effort traffic this may not be that much of a problem and one option for overcoming this is to maximize the average data rates. In case of multiflow this means that a UE receives independent data streams from multiple cells simultaneously, and (HARQ/ARQ) retransmission mechanisms are used to take care of any lost packets.
However, there are also situations where such an approach of using higher data rates is not beneficial and may even be harmful. Furthermore, higher data rates are not always preferred, but better robustness and lower latency may be desired. Examples of such situations may be communications comprising traffic types like VoIP, interactive games, or certain RRC control messages. For this type of traffic the conventional multiflow transmission where data is routed to the UE over separate network elements such as separate cells under certain circumstances does not offer any improvements. In fact it may even lead to worse performance since traffic possibly gets more often transmitted over a weaker link. It is to be noted that multiflow typically leads to higher throughput, and therefore lower latency, by virtue of having the possibility of using two links in parallel. However, a worse performance may happen for very short messages which run over only one link, in case the link happens to be the weaker link.